Hypersonic scramjet engine fuel injector

ABSTRACT

A hypersonic scramjet engine fuel injector and a hypersonic scramjet engine having such a fuel injector. The engine has a serially connected inlet, combustor, and exhaust nozzle. Multiple, horizontally-spaced-apart fuel injectors are positioned in and connected to the combustor&#39;s top portion. Each fuel injector has a hollow wedge shape housing. To improve fuel-air mixing for better combustion, the housing&#39;s end wall has multiple, discrete, convergent-divergent fuel outlet nozzles and its side walls have horizontally-extending exterior grooves. Fuel is used to cool the fuel injector housing with the housing&#39;s bottom and side walls having fuel-exit holes and the housing having an interior serpentine fuel passageway.

The United States Government has rights in this invention pursuant toContract Number F33657-86-C-2136 between the U.S. Air Force and theGeneral Electric Company.

This is a division of application Ser. No. 245,181, filed Sept. 16, 1988now U.S. Pat. No. 4,903,480.

BACKGROUND OF THE INVENTION

The present invention relates generally to scramjet engines and moreparticularly to a fuel injector for a hypersonic flight vehicle scramjetengine.

At hypersonic Mach numbers (i.e., greater than Mach 5) a flight vehiclehaving an air breathing engine, such as a scramjet, requires an enginecombustion chamber (also known as a combustor) having a large frontalcross-sectional area. In scramjet engine design, it is important todistribute the fuel, such as pressurized hydrogen gas, uniformly overthis area for proper combustion. It is noted that injecting the fuelinto the combustor itself provides thrust apart from the thrust createdby the fuel combustion. In commonly assigned and copending U.S. patentapplication Ser. No. 828,844 entitled "Ramjet/Scramjet Engine" by DANIELJ. Lahti et al., filed Jan. 2, 1986, there is shown a scramjet enginehaving an array of horizontally-spaced fuel injectors each with a wedgeshape wherein the fuel exits a single convergent-divergent fuel outletnozzle (a single-wall-slot fuel injector) into the combustor. Combustordesign is always concerned with proper mixing of the fuel and the inletair for uniform combustion. As the engine inlet compresses (and thereforheats) the incoming air and as the incoming air impinges upon the fuelinjector at hypersonic speeds (and therefor frictionally heats the fuelinjector), there also is the problem of cooling the fuel injector so asto prolong component life and/or allow the use of materials that wouldfail without cooling.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a hypersonic scramjet enginefuel injector which promotes mixing of the fuel with the engine inletair.

It is another object of the invention to provide a hypersonic scramjetengine fuel injector which is cooled for protection against thehypersonic-speed impingement of the compressed inlet air.

It is an additional object of the invention to provide a hypersonicscramjet engine for such a fuel injector.

In the first through the fourth embodiments of the invention claimed asa fuel injector, the hypersonic scramjet engine fuel injector commonlyincludes a right-triangular-wedge-shaped, fuel-tight housing having aright-triangular cross section defined by the following attached walls:a horizontal top wall with a fuel inlet orifice, an inclined bottomwall, and a vertical end wall. Two right-triangular-shaped vertical sidewalls are attached to the previously-mentioned walls to complete thehousing.

In the first embodiment, the fuel injector's end wall also has at leasttwo discrete, vertically-spaced-apart convergent-divergent fuel outletnozzles.

In the second embodiment, the fuel injector's end wall has aconvergent-divergent fuel outlet nozzle, and the side walls have atleast two vertically-spaced apart, horizontally-extending exteriorgrooves which deepen towards, and reach, the end wall.

In the third embodiment, the fuel injector's end wall has aconvergent-divergent fuel outlet nozzle, and at least one of the bottomand side walls has at least two spaced-apart fuel-exit holes.

In the fourth embodiment, the fuel injector's end wall has aconvergent-divergent fuel outlet nozzle, and its fuel inlet orifice isdistal its end wall. The fuel injector also includes at least twospaced-apart interior walls inside the housing connected to the sidewalls to create a fuel passageway having a serpentine-shaped crosssection with a straight segment from the inlet orifice along a majorityof the bottom wall.

In the fifth through the eighth embodiments of the invention claimed asan engine, the hypersonic scramjet engine commonly includes an inlet, acombustor serially connected to the inlet's aft portion, an exhaustnozzle serially connected to the combustor, and at least twohorizontally-spaced-apart fuel injectors positioned in the combustor andconnected to the combustor's top portion. Each fuel injector's bottomwall is coplanar and coextensive with the inlet's inclined upper wall.

The fifth embodiment engine employs first embodiment fuel injectors, thesixth embodiment engine employs second embodiment fuel injectors, theseventh embodiment engine employs third embodiment fuel injectors, andthe eighth embodiment engine employs fourth embodiment fuel injectors.

Several benefits and advantages are derived from the invention. Themultiple fuel outlet nozzle and the side-wall groove features of theinvention each promote better mixing of the fuel with the air forimproved combustion. The side/bottom wall fuel-exit hole and serpentineinternal fuel passageway features of the invention each provide coolingby the fuel of the fuel injector's bottom and side walls in athermally-harsh hypersonic environment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate several embodiments of the presentinvention wherein:

FIG. 1 is schematic diagram of the invention showing the hypersonicscramjet engine including its fuel injector;

FIG. 2 is a perspective partial view of the engine of FIG. 1 showing anarray of fuel injectors connected to the top portion of the engine'scombustor;

FIG. 3 is a side-elevational cross-sectional view of one design of oneof the fuel injectors of FIG. 2;

FIG. 4 is a top plan view of the fuel injector of FIG. 3;

FIG. 5 is a back-elevational view of the fuel injector of FIG. 3;

FIG. 6 is a side-elevational cross-sectional view of an alternate designof one of the fuel injectors of FIG. 2;

FIG. 7 is a cross-sectional view taken along lines 7--7 of FIG. 6;

FIG. 8 is a side-elevational view of another alternate design of one ofthe fuel injectors of FIG. 2; and

FIG. 9 is a back-elevational view of the fuel injector of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, as embodied in a hypersonic scramjet engine 10and a fuel injector 12, is illustrated generally in FIGS. 1 and 2, withparticular alternate designs of the fuel injector 12 shown in FIGS. 3-5,6-7, and 8-9. The hypersonic scramjet engine 10 includes an inlet 14, acombustor 16, an exhaust nozzle 18, and a plurality ofhorizontally-spaced-apart fuel injectors 12, as shown in FIGS. 1 and 2.Ignitors (not shown) could be added in the combustor if the fuel werenot self-igniting, as is known to those skilled in the art. Thecombustor 16 is serially connected to the aft portion 20 of the inlet14, while the exhaust nozzle 18 is serially connected to the combustor16. The fuel injectors 12 are disposed in the combustor 16 and areconnected to the top portion 22 of the combustor 16. The inclined bottomwall 24 of each fuel injector 12 is generally coplanar and coextensivewith the inclined upper wall 26 of the inlet 14.

In a first embodiment of the invention, best seen in FIGS. 2-5, eachhypersonic scramjet engine fuel injector 12 includes a housing 28 havinga generally horizontal top wall 30, the previously mentioned inclinedbottom wall 24, and a generally vertical end wall 32 which are attachedtogether to define in cross section a generally right triangle. Thisright-triangle shape is the shape of two vertical side walls 34 whichalso make up the housing 28. The side walls 34 are attached to the top30, bottom 24, and end 32 walls to define a fuel-tight, generallyright-triangular hollow wedge which is the fuel injector housing 28. Thetop wall 30 of the fuel injector housing 28 has a fuel inlet orifice 36,and the end wall 32 has a plurality of discrete, vertically-spaced-apartconvergent-divergent fuel outlet nozzles 38. Each supersonic fuel outletnozzle 38 can be either circular or elliptical.

Additional thrust is provided by the fuel, apart from combustion, as thefuel issues through the multiple fuel outlet nozzles 38 at supersonicvelocities in a direction generally parallel to the engine airflow. Thediscrete fuel outlet nozzles 38 distribute the fuel without obstructingthe flowpath. The base areas 40 around each fuel outlet nozzle 38provide recirculation zones which act as sources of free radicals andheat to ignite the fuel-air mixture. Thus, the base areas 40 act asflame holders without the use of steps in the flowpath. These featuresimprove the efficiency of the combustion process and thrust production.The discrete fuel outlet nozzles 38 provide better fuel distributionthan does a single-wall-slot fuel injector.

In a preferred configuration, as seen in FIG. 9, the fuel outlet nozzle38a closest the bottom wall 24 is canted, with respect to the end wall32, toward the bottom wall 24. Also, one fuel outlet nozzle 38b iscanted, with respect to the end wall 32, generally-horizontally towardone of the side walls 34 while an adjacent fuel outlet nozzle 38c iscanted, with respect to the end wall 32, generally-horizontally towardthe other of the side walls 34. The canted fuel outlet nozzles 38a, 38b,and 38c remain generally parallel to the engine airflow, the degree oftilt being small but sufficient to increase the mixing of the fuel,exiting the fuel outlet nozzles 38, with the air to improve combustion.

In an exemplary configuration, as seen in FIG. 6, the fuel injector 12also includes a plurality of spaced-apart, generally parallel, andgenerally-horizontally-oriented interior walls 42. These horizontalinterior walls 42 are disposed within the fuel injector housing 28 andare connected to the side walls 34 to define fuel guideways 44. Theyalso are spaced from the bottom wall 24 and extend to the end wall 32 ofthe housing 28. The horizontal interior walls 42 act to channel the fueltowards the fuel outlet nozzles 38 in a direction parallel to the engineairflow.

In a second embodiment of the invention, as seen in FIGS. 8 and 9together with FIGS. 2-5, each hypersonic scramjet engine fuel injector12 includes the elements of the first embodiment previously discussed,with the exception that the second embodiment may have an end wall 32with a single convergent-divergent fuel outlet nozzle (asingle-wall-slot fuel injector) or it may have a plurality of discrete,vertically-spaced-apart convergent-divergent fuel outlet nozzles 38. Inthe second embodiment, the fuel injector side walls 34 have a pluralityof vertically-spaced-apart, generally-horizontally-extending exteriorgrooves 46 which deepen towards and reach the end wall 32. The exteriorgrooves 46 receive a volume of the compressed inlet air moving past thefuel injector housing 28, such volume thereby having imparted to it atransverse velocity component which better mixes such air with the fuelfrom the end wall fuel outlet nozzles 38 for improved combustion.Fuel-air mixing also is enhanced due to the vortices produced by thescarf edges. In a preferred configuration, the exterior grooves 46 alsowiden toward the end wall 32 for better air-fuel mixing. In an exemplaryconfiguration which facilitates manufacture, each exterior groove 46 hasa generally-horizontally-extending centerline 48 and two mirror imageplanar groove surfaces 50 connected to the centerline 48 with eachgroove surface 50 having the shape of a general right triangle.

In a third embodiment of the invention, as seen in FIGS. 6 and 7together with FIGS. 2-5, each hypersonic scramjet engine fuel injector12 includes the elements of the first embodiment previously discussed,with the exception that the third embodiment (like the secondembodiment) may have an end wall 32 with a single convergent-divergentfuel outlet nozzle (a single-wall-slot fuel injector) or it may have aplurality of discrete, vertically-spaced-apart convergent-divergent fueloutlet nozzles 38. In the third embodiment, at least one wall of thebottom 24 and side 34 walls of the fuel injector 12 has a plurality ofspaced-apart fuel-exit holes 52. Preferably, the fuel-exit holes 52 arelocated in the bottom wall 24, or in each side wall 34, or in each ofthe bottom and side walls. The fuel also acts as the coolant. Theexterior surfaces of the bottom 24 and/or side 34 walls are cooled bythe fuel from the fuel-exit holes 52 which provides external filmcooling resulting in better thermal protection for the fuel injectorhousing 28. Another advantage of the fuel-exit holes 52 is the reductionof air friction on the external surfaces due to the cooling film. Inaddition, the cooling film provides a means for fueling part of the airflow between the fuel injectors 12 in the scramjet engine 10, thusincreasing mixing of fuel and air.

In the fuel injector configuration having fuel-exit holes 52a in a sidewall 34, as seen in FIGS. 6 and 7, the holes 52a preferably are canted,with respect to the side wall 34, toward the end wall 32. Canting theside-wall fuel-exit holes 52a towards the end wall 32 results in aportion of the exiting fuel being recovered as engine thrust apart fromcombustion.

In the fuel injector configuration having fuel-exit holes 52b in thebottom wall 24, as seen in FIG. 6, the holes 52b preferably aregenerally perpendicular to the bottom wall 24. Such bottom-wallfuel-exit holes 52b facilitate manufacture.

In an alternate configuration, the fuel injector 12 also includes adeflector 54 connected to the housing's bottom wall 24 by multiple tabmembers 56 so as to leave a space 58 between the deflector 54 and bottomwall 24. The deflector 54 is positioned near the bottom-wall fuel-exitholes 52c and is large enough to at least span the holes 52c. In anexemplary configuration, the deflector 54 is also attached to the frontof the bottom wall 24 (see FIG. 6) and transversely spans the side walls34 (see FIG. 7) to provide a shield from the inlet air for the coolingfilm of fuel exiting the fuel exit holes 52 in the bottom 24 and side 34walls. Without the shield the cooling film would be dispersed morequickly by the inlet air. With the deflector 54 present, all theperpendicular fuel-exit holes 52b shown in FIG. 6 are preferablyreplaced with fuel-exit holes 52c which are generally horizontal andtherefor generally parallel to the top wall 30. The horizontal holes 52cprovide better impingement cooling of the fuel on the deflector 54.Without a deflector 54 present, the perpendicular fuel-exit holes 52b ofFIG. 6 are preferably substituted for the horizontal fuel-exit holes52c.

In a fourth embodiment of the invention, as seen in FIGS. 2-5, eachhypersonic scramjet engine fuel injector 12 includes the elements of thefirst embodiment previously discussed, with the exception that thefourth embodiment (like the second and third embodiments) may have anend wall 32 with a single convergent-divergent fuel outlet nozzle (asingle-wall-slot fuel injector) or it may have a plurality of discrete,vertically-spaced-apart convergent-divergent fuel outlet nozzles 38. Inthe fourth embodiment, as seen in FIG. 3, the fuel injector 12 alsoincludes a plurality of spaced-apart, generally parallel, inclinedinterior walls 60 which are also generally parallel to the bottom wall24. These inclined interior walls 60 are disposed within the fuelinjector housing 28 and are connected to the side walls 34 to define afuel passageway 62 which has a serpentine-shaped cross section with agenerally straight segment 64 from the injector top wall fuel inletorifice 36, which is distal the end wall 32, along a majority portion ofthe injector bottom wall 24. Thus the serpentine fuel passageway 62directs the fuel to first cool the interior surface of the bottom wall24 upon whose aerodynamically-heated exterior surface the inlet airflowimpinges.

In a preferred configuration, as seen in FIG. 3, the fuel injector 12also includes a multiplicity of angled, turbulence-promoting ribs 66positioned within the fuel passageway 62 and connected to at least onewall of the bottom 24 and inclined interior 60 walls. Preferably, theribs 66 are connected to the bottom wall 24, or to each inclinedinterior wall 60, or to each of the bottom and inclined interior walls.The ribs 66 produce the vortex shedding and the swirl flow to enhancethe cooling effectiveness.

In an exemplary configuration, as seen in FIGS. 3 and 4, the fuelinjector top wall 30 has a fuel outlet orifice 68 near the end wall 32and in communication with the fuel passageway 62, and the top wall 30also has a fuel inlet opening 70 positioned between the fuel outletorifice 68 and the end wall 32. Also, a fuel-passageway-boundinginterior back wall 72 angles towards the end wall 32 extending from thetop wall 30, between the fuel outlet orifice 68 and the fuel inletopening 70, to the bottom wall 24.

Obviously, the previously-discussed first four embodiments of theinvention can exist in various combinations in the same fuel injector,as can be appreciated by those skilled in the art.

In a preferred configuration, the hollow, thin-wall, lightweight fuelinjector housing 28 is cast as an integral piece to be cost effectiveand to eliminate leakage. Current casting technology allows even theturbulence-promoting ribs 66 to be part of the integral housing 28, ascan be appreciated by the artisan from a reading of U.S. Pat. Nos.4,514,144 and 4,627,480 (each entitled "Angled Turbulence Promoter",each by Ching-Pang Lee, and each respectively issued Apr. 30, 1985 andDec. 9, 1986). The previously-discussed deflector 54 and tab members 56may be discrete parts with attachment to the fuel injector housing 28accomplished by welding. The fuel, fuel tank, any fuel pressurizationsystem, and the fuel conduits leading to the fuel injector housing'sinlet orifice 36 do not form a part of the previously-discussed firstfour or any other embodiments of this invention, but are known to thoseskilled in the art to use with this invention.

In a fifth through eighth embodiment of the invention, thepreviously-described scramjet engine 10 employs a respective one of thefuel injectors 12 of the previously-described first through fourthembodiments of the invention.

The foregoing description of several preferred embodiments of theinvention has been presented for purposes of illustration. It is notintended to be exhaustive or to limit the invention in the precise formdisclosed, and obviously many modifications and variations are possiblein light of the above teaching. It is noted that the terms "upper" and"lower", "horizontal" and "vertical", and the like, are terms ofconvenience used to describe the elements of the scramjet engine 10 andfuel injector 12. For example, it is clear that the fuel injector 12 canbe oriented, with respect to the rest of the hypersonic scramjet engine10, at any pre-chosen angle about the engine's longitudinal axis andthat the scramjet engine 10 can be oriented, with respect to the rest ofa hypersonic flight vehicle (not shown) at any pre-selected angle aboutthe vehicle's longitudinal axis. In preferred embodiments of theinvention, the previously-listed terms describe the elements of the fuelinjector 12 and scramjet engine 10 when its associated hypersonic flightvehicle is in level flight. It is intended that the scope of theinvention be defined by the claims appended hereto.

We claim:
 1. A hypersonic scramjet engine fuel injector comprising ahousing having a generally horizontal top wall, an inclined bottom wall,and a generally vertical end wall attached together to define in crosssection a generally right triangle, said housing also having twogenerally vertical side walls having a said-generally-right-triangleshape, said side walls attached to said top, bottom, and end walls todefine a fuel-tight, generally right-triangular wedge, said top wallhaving a fuel inlet orifice, said end wall having a convergent-divergentfuel outlet nozzle, and said side walls having a plurality ofvertically-spaced-apart, generally-horizontally-extending exteriorgrooves deepening towards and reaching said end wall.
 2. The fuelinjector of claim 1, wherein said grooves also widen toward said endwall.
 3. The fuel injector of claim 2, wherein each said groove has agenerally-horizontally-extending centerline and two mirror image planargroove surfaces connected thereto, each said groove surface having agenerally right-triangle configuration.
 4. A hypersonic scramjet enginecomprising:(a) an inlet having an inclined upper wall and having an aftportion; (b) a combustor serially connected to said aft portion of saidinlet, said combustor having a top portion; (c) an exhaust nozzleserially connected to said combustor; and (d) a plurality ofhorizontally-spaced-apart fuel injectors disposed in, and connected tosaid top portion of, said combustor, each said fuel injector including ahousing having a generally horizontal top wall, an inclined bottom wall,and a generally vertical end wall attached together to define in crosssection a generally right triangle, said housing also having twogenerally vertical side walls having a said-generally-right-triangleshape, said side walls attached to said top, bottom, and end walls todefine a fuel-tight, generally right-triangular wedge, said top wallhaving a fuel inlet orifice, said end wall having a convergent-divergentfuel outlet nozzle, and said side walls having a plurality ofvertically-spaced-apart, generally-horizontally-extending exteriorgrooves deepening towards and reaching said end wall, wherein saidbottom wall of each said fuel injector is generally coplanar andcoextensive with said upper wall of said inlet.